function toggleAudio() {
  const audio = document.getElementById("bgm");
  if (audio.paused) {
    audio.play();
    document.getElementById("playBtn").innerText = "🔈 音乐播放中";
  } else {
    audio.pause();
    document.getElementById("playBtn").innerText = "🎵 点击播放音乐";
  }
}